Migrations, breeding, and growth inPomatoschistus minutus(Pallas) (Pisces, Gobiidae) in Oslofjorden, Norway

Abstract

Aspects of the biology of the sand goby were studied over a period of 21 months. The goby is common in the littoral from April (at temperatures above 3° C) to July, when breeding takes place, and from September to December, when the somatic growth occurs. At temperatures above 19° C and below 4–5° G the goby is rare in the littoral. The growth is very rapid, the 0-group fish reaching almost the length of the 1-group fish during their first growing season. Growth is faster than in other populations from similar latitudes, suggested to be due to eutrophication. Spawning occurs even in less than 1 m depth. There is art indication that light intensity, together with temperature, is important for breeding to start. The food consists of any organism of appropriate size and texture. Polychaetes are a conspicuous component. Feeding occurs intensively all through the stay in the littoral, but is lower during the breeding season. Various features of the biology of the sand goby in Oslofjorden appear to be simple and more clearcut when compared to other populations studied, probably due to the stable and predictable environmental conditions.